1. Field of the Invention
The present invention relates to a radio telephone apparatus having a base unit and a radio telephone unit connected to the base unit via a radio communication link and to a method of controlling the same, and more particularly to a radio telephone apparatus having an instantaneous conversation function which makes it possible to effect a shift to a conversation state simply by lifting the radio telephone unit off a radio telephone unit-mounting base in a standby state.
2. Description of the Related Art
Conventionally, this type of radio telephone apparatus is arranged as shown in FIG. 6.
In FIG. 6, a base unit 1 is connected to a radio telephone unit 2 via a radio communication link and is also connected to a wire telephone line 3.
A signal transmitted from the wire telephone line 3 is inputted to a transmitter 5 via a hybrid circuit 4 so as to be subjected to modulation.
Radio waves modulated by the transmitter 5 are transmitted to the radio telephone unit 2 via a transmission antenna 6.
Meanwhile, the radio waves transmitted from the radio telephone unit 2 are received by a reception antenna 7 and are demodulated by a receiver 8, and are then transmitted to the wire telephone line 3 via the hybrid circuit 4.
A synthesizer 9 outputs a frequency corresponding to a radio channel to both the transmitter 5 and the receiver 8.
One output of the receiver 8 is inputted to a received electric field detecting circuit 10 so as to determine an electric field strength thereof.
This circuit is generally referred to a carrier squelch circuit or a noise squelch circuit.
In addition, another output of the receiver 8 is delivered as a data signal included in the received and demodulated waves, and is inputted to an identification signal detecting circuit 11 for collating an identification signal determined through a combination of the base unit 1 and the radio telephone unit 2, so as to undergo collation.
This identification signal is generally referred to as an ID code.
An output of the received electric field detecting circuit 10 and the demodulated output of the data signal are inputted to a control circuit 12 so as to be used for connection control.
Furthermore, the control circuit 12 effects other control such as control of the radio channel by controlling the synthesizer 9 as well as transmission of a transmission data signal to the transmitter 5 as an input for modulation.
Similarly, the radio telephone unit 2 is also provided with a reception antenna 13 and a receiver 14, and its modulated output is delivered to a telephone receiver 15.
In addition, voice inputted through a telephone transmitter 16 is inputted to a transmitter 17 so as to undergo modulation and is transmitted to the base unit 1 via a transmission antenna 18 in the form of radio waves.
A synthesizer 19, a received electric field detecting circuit 20, an identification signal detecting circuit 21 are arranged in the same way as those of the base unit 1, and a control circuit 22 effects the control of the radio telephone unit 2.
A speaker 23 is a sounder for issuing a ringing tone when an incoming call is received.
A talk commencing/terminating key 24 is so arranged that a command for commencing a conversation and a command for terminating the conversation can be inputted alternately each time it is pressed once.
A battery 25 is used as a power source for the radio telephone unit 2, and this battery 25 is charged by a charger 30 via a charging terminal 26. Here, the charger 30 functions as a base for mounting the radio telephone unit 2.
A charging detection circuit 27 is connected to a charging route for the battery 25 so as to detect whether the battery 25 is being charged or not, i.e., whether the radio telephone unit 2 is placed on the charger 30, i.e., the mounting base, or has been lifted off the charger 30, i.e., the mounting base.
With the above-described conventional radio telephone apparatus, when an incoming call is received by the base unit 1 via the wire telephone line 3 in a standby state, a ringing tone is issued from the speaker 23 of the radio telephone unit 2 or the base unit 1.
At this time, in the case of the radio telephone unit 2, it is possible to respond to the incoming call by pressing the talk commencing/terminating key 24.
In addition, it is also possible to respond to the call by lifting the radio telephone unit 2 off the charger 30.
The function whereby a conversation state can thus be established immediately upon lifting the radio telephone unit 2 off the charger 30 without pressing the talk commencing/terminating key 24 is called an instantaneous conversation function and is incorporated into many radio telephone apparatus today.
Accordingly, a brief description will be given of control of the instantaneous conversation function.
As described above, the charging detection circuit 27 detects a voltage at the charging terminal 26 which is in contact with the charger, and then outputs a detected result to the control circuit 22.
As a result, by monitoring the detected output of the charging detection circuit 27, the control circuit 22 is capable of ascertaining whether or not the radio telephone unit 2 is being charged.
Generally, in cases where a response to a call is made by lifting the radio telephone unit 2, at a point of time when the radio telephone unit 2 is lifted, the charging terminal 26 is disconnected from the charger, and the state of the radio telephone unit 2 shifts from that of being charged to that of not being charged.
Accordingly, the control circuit 22 may ascertain that a responding operation has been effected when the detected output of the charging detection circuit 27 has shifted from the state of being charged to that of not being charged. If a communication channel is formed at that time, a conversation state is established immediately, thereby making it possible to realize the aforementioned instantaneous conversation function.
FIG. 7 illustrates an example of the general operation of a conventional radio telephone apparatus having the instantaneous conversation function and the talk commencing/terminating key 24.
In FIG. 7, when the radio telephone unit 2 is in a standby state (Step 501), on the basis of the detected output of the charging detection circuit 27 the control circuit 22 determines whether the state of the radio telephone unit 2 has shifted from that of being charged to that of not being charged (Step 502).
Then, while the radio telephone unit 2 is being charged, the standby state is maintained, when the state has shifted to that of not being charged, the operation proceeds to a talking operation by means of the instantaneous conversation function (Step 503).
After the conversation state is thus established, the control circuit 22 determines whether or not the talk commencing/terminating key 24 has been pressed (Step 504).
Then, while the talk commencing/terminating key 24 is not being pressed, the conversation state is maintained, but when it is pressed, a talk terminating operation is effected immediately (Step 505) to return to the original standby state (Step 501).
With the conventional radio telephone apparatus controlled in the manner described above, no problem is presented when a response is made by pressing the talk commencing/terminating key 24 in the standby state. However, in cases where a response is made by lifting the radio telephone unit 2 by means of the instantaneous conversation function, there has been a danger of immediately resulting in the talk terminating operation if the talk commencing/terminating key 24 is pressed by mistake immediately after the conversation state is established.
Thus, with the above described conventional radio telephone apparatus, in cases where the instantaneous conversation function and the talk commencing/terminating key are used jointly, the call is terminated immediately if the talk commencing/terminating key is pressed by mistake immediately after the conversation state is established by means of the instantaneous conversation function. Hence, it has been necessary to pay utmost care not to erroneously operate the talk commencing/terminating key when the radio telephone unit is lifted, so that there has been the problem that the operating efficiency is bound to decline.